A Study of the O⁴⁺Emissivity Profiles with Two Separate Photon Emissivity Coefficient Databases and a Comparison of the Impurity Diffusion Coefficients in the Aditya Tokamak

Abstract

The present study is an analysis between radial emissivity profiles of the 650.024 nm transition of the O 4+ ion obtained using two separate Photon Emissivity Coefficient (PEC) databases. Emissivity values of the 650.024 nm O 4+ transition in visible-spectral region have been experimentally obtained for the Aditya tokamak. The radial number density distributions of different charge states of oxygen are estimated using a semi-implicit numerical method applied over the radial impurity transport equation. The 650.024 nm emissivity is calculated using the obtained impurity number density and with PECs from two separate databases namely the ADAS (Atomic Data and Analysis Structure) and the NIFS (National Institute for Fusion Science) database. Although impurity diffusivity profiles must not be dependent upon the choice of PEC databases; yet a requirement of separate impurity (oxygen) diffusivity profiles for the two PEC databases is observed, such that their corresponding calculated O 4+ emissivities best depict the experimental emissivity data. A difference in the ionization and recombination rate coefficients provided in the ADAS and NIFS databases can lead to discrepancies in the impurity number densities calculated. The effects upon the impurity diffusivity while using ionization and recombination rate coefficients from two separate databases are further studied.

Evaluation of an Oxygen Transport Coefficient in the Aditya Tokamak Using the Radial Profile of O4+ Emissivity and the Importance of Atomic Data Used Therein

“…Experimental profiles from both the high and low field sides were matched with simulated profiles by varying the diffusion coefficient and impurity source rate. For modeling purposes, at first the experimental profile of the low field side was matched with a diffusion coefficient profile, and then STRAHL code was again run to obtain best-fit for the high field side separately, as discussed in details in the paper by Chowdhuri et al [17]. The simulated best-fit emissivity profiles obtained using code in both the low and high field sides of the Aditya tokamak plasma to the measured profiles are represented by a line in the figure.…”

“…The radial profile of this emission was also employed to validate the impurity transport code developed using a semi-implicit numerical technique for the study of impurity transport in tokamak plasmas [16]. Later, the O 4+ emissivity profile was modeled using this code [17], in which the PEC data were taken from ADAS and from a CRM code [10] developed by the National Institute of Fusion Science (NIFS), Japan. In this paper, the oxygen transport was studied using STRAHL code and the two above-mentioned PEC data to understand the role of atomic data used in impurity transport modeling.…”

Physics studies of ADITYA & ADITYA-U tokamak plasmas using spectroscopic diagnostics

“…Various studies on the impurities behaviour and plasma properties, such as impurity influx, reduction of plasma Z eff after Li coating of wall, etc, have been regularly carried out using diagnostics based on PMT (photomultiplier tube), PMT array, and the multiple PMT modules in the visible range. The plasma ion temperature, rotation and spatial profile of brightness measurement have been done routinely using a high-resolution spectrometer having 1 m focal length and equipped with a CCD (charge coupled device) camera [22] to understand the physical mechanism behind intrinsic rotation [23] and to study the impurity transport [24][25][26], respectively. A fast visible imaging camera coupled with a fiber bundle has been also used to measure the plasma shape and size and also to study the plasma disruption.…”

Study of increment of emission intensity in a cold atmospheric pressure helium plasma jet using the ADAS

“…The collisional-radiative (CR) model is used to study in various types of plasmas [19][20][21][22][23]. The CR model works well in the intermediate density regime i.e., ∼ 10 10 -10 15 cm −3 .…”

“…The CR model of the ADAS code and database has been used for the study of the laser plasma, the tokamak plasma, etc. [19][20][21][22][23]. The ADAS is an interconnected set of computer codes and data collections for modelling the radiating properties of ions and atoms in plasmas.…”